This invention generally relates to synthetic nonwoven materials fabricated by wet-laid processes. In particular, the invention relates to a paper-like web made with polyester fibers which is useful as a thermoformable liner material for framed structures, such as an office partition.
A typical office partition construction involves laminating several different components together, with each component providing a specific functionality to the structure. Most of such structures use fiberglass mats which have been impregnated with phenolic or other thermosetting saturants to impart the desired rigidity to the structure. Such laminated structures are unnecessarily complicated and are not completely recyclable. There is a need for an improved office partition construction having fewer components.
An improved office partition comprises a rigid frame, e.g., a wooden panel, and a woven fabric which is attached to the wooden panel. There is a need for completely recyclable and environmentally friendly means for attaching the woven fabric to the wooden panel.
The present invention is a rigid thermoformable recyclable nonwoven liner material which is formed by a wet process on a papermaking machine. The wet-laying process is most suitable for this application as compared to other existing forming technologies due to the resulting uniformity in structure and tight construction. This invention also has the benefit of eliminating the manufacturing costs associated with dry web formation. The rigid thermoformable nonwoven liner material is intended to be laminated to a woven fabric and then thermomolded around a wooden panel to form an office partition. The paper-like construction is most beneficial in order to meet the tackability (i.e., tack-holding) requirement for the substrate.
The wet-laying process may consist entirely of conventional steps. The fiber furnish includes thermoplastic matrix fibers and thermoplastic binder fibers. In accordance with the preferred embodiment, the matrix fibers are made of polyester and the binder fibers are bicomponent fibers having co-polyester sheaths and polyester cores. The use of polyester is advantageous in that polyester is considered to be flame retardant in nature. The bicomponent fibers serve two purposes. First, the low melting point of the co-polyester enables bonding and therefore provides sufficient strength for on-line processing and handling during substrate manufacture. Second, the co-polyester sheath material is moldable at a lower temperature compared to the matrix polyester fibers.
In accordance with one preferred embodiment of the method of manufacturing a nonwoven liner material for use as a thermoformable liner in an office partition, the web of fibers coming off the papermaking machine is passed through a first binder application station, which applies a water-based solution, emulsion or foam having binder dispersed therein to one side of the web. In accordance with the preferred embodiment, the binder consists of polyvinyl chloride. The polyvinyl chloride binder features a curing mechanism which is activated by heat. The curing temperature of polyvinyl chloride is in the range of 225xc2x0 to 280xc2x0 F. Curing above 250xc2x0 F. imparts the wet strength and the rigidity desired for the product. Alternatively, the binder can be polyvinylidene chloride or polyester.
The treated web exits the first binder application station and enters an infrared dryer comprising a plurality of infrared heaters which remove moisture from the web. Additional moisture is removed by passing the web through a first section of dryer cans. The dryer cans are heated to a temperature of about 300xc2x0 F. Since the polyester sheath of the binder fiber has a melting point in the range of 225xc2x0 to 240xc2x0 F., the binder fibers are activated, i.e., the sheaths are melted, as the web passes over the dryer cans. Also the binder, which has a film forming temperature of 150xc2x0 F. and a curing temperature ranging from 225xc2x0 to 240xc2x0 F., is activated.
After drying in the first section of dryer cans, the web passes through a second binder application station, which again applies a water-based solution, emulsion or foam to the web. The water-based solution, emulsion or foam has the same type of binder particles as those applied during the first binder application. The web is then passed through a second section of dryer cans to again remove moisture. The temperature of the dryer cans in the second section is about 300xc2x0 F. Again the binder fiber sheath material is melted and the binder is activated as the web passes over the dryer cans. Upon cooling of the web, the binder fiber sheath material is fused to neighboring matrix fibers. The web is then wound on a winder roll. Optionally, the dried web is calendered using unheated calender rolls prior to winding.
The final product is a 100% recyclable, 100% thermoplastic nonwoven liner material. Being 100% thermoplastic in nature, the final product can be molded in a wide range of temperatures ranging from 225xc2x0 to 300xc2x0 F.